• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3547-3552
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• 2014

Laser Raman spectroscopy is one of the most powerful technologies for standoff detection of hazardous materials including explosives. Supported by recent development of laser and sensitive ICCD camera, the technology can identify trace amount of unknown substances in a distance. Using this concept, we built a standoff detection system, in which nanosecond pulse laser and nanosecond gating ICCD technique were delicately devised to avoid the large background noise which suppressed weak Raman signals from the target sample. In standoff detection of explosives which have large kill radius, one of the most important technical issues is the detection distance from the target. Hence, we focused to increase the detection distance up to 54 m by careful optimization of optics and laser settings. The Raman spectra of hazardous materials observed at the distance of 54 m were fully identifiable. We succeeded to detect and identify eleven hazardous materials of liquid or solid particles, which were either explosives or chemical substances used frequently in chemical plants. We also performed experiments to establish the limit of detection (LOD) of HMX at 10 m, which was estimated to be 6 mg.

• Bulletin of the Korean Chemical Society
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• 제34권6호
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• pp.1668-1672
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• 2013

We developed a standoff Raman detection system for explosive molecules (EMs). Our system was composed of reflective telescope with 310 mm diameter lens, 532 nm pulse laser, and Intensified Charge-Coupled Device (ICCD) camera. In order to remove huge background noise coming from ambient light, laser pulses with nanosecond time width were fired to target sample and ICCD was gated to open only during the time when the scattered Raman signal from the sample arrived at ICCD camera. We performed standoff experiments with military EMs by putting the detector at 10, 20 and 30 m away from the source. The standoff results were compared with the confocal Raman results. Based on our standoff experiments, we were able to observe the peaks in the range of 1200 and $1600cm^{-1}$, where vibrational modes of nitro groups were appeared. The wave numbers and shapes of these peaks may serve as good references in detecting and identifying various EMs.

• 한국군사과학기술학회지
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• 제18권5호
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• pp.612-620
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• 2015

Short-range detection of chemical agents deposited on ground surface using a standoff Raman system employing a pulsed laser at 248 nm is described. Mounted in a vehicle such as an NBC reconnaissance vehicle, the system is protected against toxic chemicals. As most chemicals including chemical warfare agents have unique Raman spectra, the spectra can be used for detecting toxic chemicals contaminated on the ground. This article describes the design of the Raman spectroscopic system and its performance on several chemicals contaminated on asphalt, concrete, sand, etc.

• 한국군사과학기술학회지
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• 제24권4호
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• pp.374-381
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• 2021

Raman spectrometers are studied and developed for the military purposes because of their nondestructive inspection capability to capture unique spectral features induced by molecular structures of colorless and odorless chemical warfare agents(CWAs) in any phase. Raman spectrometers often suffer from random noise caused by their detector inherent noise, background signal, etc. Thus, reducing the random noise in a measured Raman spectrum can help detection algorithms to find spectral features of CWAs and effectively detect them. In this paper, we propose a denoising autoencoder for Raman spectra with a loss function for sample efficient learning using noisy dataset. We conduct experiments to compare its effect on the measured spectra and detection performance with several existing noise reduction algorithms. The experimental results show that the denoising autoencoder is the most effective noise reduction algorithm among existing noise reduction algorithms for Raman spectrum based standoff detection of CWAs.

• 한국군사과학기술학회지
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• 제17권1호
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• pp.8-14
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• 2014

Brightness temperature spectra acquired from FTIR(Fourier Transform Infrared)-SCADS (Standoff Chemical Agent Detection System) could be available for detection and identification of the chemical agents and pollutants from different background. IR spectrum range of 770 to 1350 $cm^{-1}$ is corresponding to "atmospheric window". A 2-dimensional(2D) brightness temperature spectrum was drawn from combining each data point through automatic continuous scanning of FTIR along with altitude and azimuth. At higher altitude, temperature of background was decreased but scattering effect of atmospheric gases was increased. Increase in temperature difference between background and blackbody in SCADS at higher temperature causes to increases in peak intensity of $SF_6$. This approach shows us a possibility that 2D visual information is acquired from scanning data with a single FTIR-SCADS.

• 한국군사과학기술학회지
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• 제23권3호
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• pp.302-309
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• 2020

Early-detection and monitoring of toxic chemical gas cloud with chemical detector is essential for reducing the number of casualties. Conventional method for chemical detection and reconnaissance has the limitation in approaching to chemically contaminated site and prompt understanding for the situation. Stand-off detector can detect and identify the chemical gas at a long distance but it cannot know exact distance and position. Chemical detection UAV is an emerging platform for its high mobility and operation safety. In this study, we have conducted chemical gas cloud detection with the stand-off chemical detector and the chemical detection UAV. DMMP vapor was generated in the area where the cloud can be detected through the field of view(FOV) of stand-off chemical detector. Monitoring the vapor cloud with standoff detector, the chemical detection UAV moved back and forth at the area DMMP vapor being generated to detect the chemical contamination. The hybrid detection system with standoff cloud detection and point detection by chemical sensors with UAV seems to be very efficient as a new concept of chemical detection.

• Current Optics and Photonics
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• 제1권3호
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• pp.247-251
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• 2017

In this study, an ultraviolet Raman spectrometer was designed and fabricated to detect chemical contamination on the ground. The region of the Raman spectrum that indicated the characteristics of the chemicals was $350-3800cm^{-1}$. To fabricate a Raman spectrometer operating in this range, the layout and angle of optical components of the spectrometer were designed using a grating equation. Experimental devices were configured to measure the Raman spectra of chemicals based on the fabricated Raman spectrometer. The wavenumber of the spectrometer was calibrated by measuring the Raman spectrum of polytetrafluoroethylene, $O_2$, and $N_2$. The spectral range of the spectrometer was measured to be 23.46 nm ($3442cm^{-1}$) with a resolution of 0.195 nm ($30.3cm^{-1}$) at 253.65 nm. After calibration, the main Raman peaks of cyclohexane, methanol, and acetonitrile were found to be similar to the references within a relative error of 0.55%.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.562-569
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• 2019

최근에 원 거리에서 폭발 물질의 감지를 위해 라만 분광 기기의 관심이 점차 증가하고 있다. 더불어 측정된 화학물질에 대한 라만 스펙트럼을 대용량 데이터베이스의 알려진 라만 스펙트라와 비교하여 식별할 수 있는 고속 검색 방법에 대한 요구도 커지고 있다. 지금까지 가장 간단하고 널리 사용되는 방법은 주어진 스펙트럼과 데이터베이스 스펙트라 사이의 유클리드 거리를 계산하고 비교하는 방법이다. 하지만 고차원 데이터의 속성으로 검색의 문제는 그리 간단하지 않다. 가장 큰 문제점중의 하나는 검색 방법에 있어서 연산량이 많아 계산 시간이 너무 오래 걸린다는 것이다. 이러한 문제점을 극복하기 위해, 우리는 정렬된 분산에 따른 MPS Sort+PDS 방법을 제안하였다. 이 방법은 벡터의 두 개의 주요한 특징으로 평균과 분산을 사용하여 후보가 될 수 없는 많은 코드워드를 계산하지 않으므로 연산량을 줄이고 계산 시간을 줄여준다. 본 논문에서 우리는 기존의 방법보다 더욱 더 향상된 2가지 새로운 방법의 고속 검색 알고리즘을 제안한다. PCA+PDS 방법은 전체 데이터를 사용하는 거리 계산과 똑같은 결과를 가지면서 PCA 변환을 통해 데이터의 차수를 감소시켜 계산량을 줄여준다. Hierarchical Cluster Tree 알고리즘은 PCA 변환된 스펙트라 데이터를 사용하여 이진 계층 클러스터 트리를 만든다. 그런 후 입력 스펙트럼과 가장 가까운 클러스터부터 검색을 시작하여 후보가 될 수 없는 많은 스펙트라를 계산하지 않으므로 연산량을 줄이고 계산 시간을 줄여준다. 실험은 정렬된 분산에 따른 MPS Sort+PDS와 비교하여 PCA+PDS는 60.06%의 성능 향상을 보였다. Hierarchical Cluster Tree는 PCA+PDS와 비교하여 17.74%의 성능향상을 보였다. 실험결과는 제안된 알고리즘이 고속 검색에 적합함을 확인시켜 준다.